Single but large high-voltage spike of brain activity that characterizes stage 2 NREM sleep.

K complex

A temporary condition in which a person is unable to move upon awakening in the morning or during the night.

sleep paralysis

A pehnomenon in which a person who is deprved of REM sleep greatly increases the amount of time spent in REM sleep at the first opportunity to sleep uninterrupted.

REM rebound

The view that sleep and dreaming are essential to normal physical and mental functioning.

restorative theory of sleep

The view that uniue sleep patterns of different aniimals evolve over time to help promote survival and environmental adaptation.

adaptive theory of sleep

also called

evolutionary theory of sleep

Serious disturbances in the normal sleep pattern that interfere with daytime functioning and cause subjective distress.

sleep disorders

A condition in which a person regularly experiences an inability to fall asleep, stay asleep, or to feel adequately rested by sleep.

insomnia

A condition in which unpleasant sensations in the lower legs are accompanied by an irrisistible urge to move the lega, temporarily relieving the unpleasant sensation but disrupting sleep.

restless legs syndrome (RLS)

A sleep disorder in which the person repeatedly stops breathing during sleep.

sleep apnea

A sleep disturbance characterized by an episode of walking or performing other actions during stage 3 or stage 4 NREM sleep.

sleepwalking

also called

somnambulism

A sleep disturbance characterized by an episode of increased physiological arousal, intense fear and panic, firghtening hallucinations, and no recall of the episode the next morning; typically occurs during stage 3 or stage 4 NREM sleep